Semiconductor processing methods of removing conductive material

ABSTRACT

The invention includes a semiconductive processing method of electrochemical-mechanical removing at least some of a conductive material from over a surface of a semiconductor substrate. A cathode is provided at a first location of the wafer, and an anode is provided at a second location of the wafer. The conductive material is polished with the polishing pad polishing surface. The polishing occurs at a region of the conductive material and not at another region. The region where the polishing occurs is defined as a polishing operation location. The polishing operation location is displaced across the surface of the substrate from said second location of the substrate toward said first location of the substrate. The polishing operation location is not displaced from said first location toward said second location when the polishing operation location is between the first and second locations. The invention also includes a semiconductor processing method of removing at least some of a conductive material from over a surface of a semiconductive material wafer. A polishing pad is displaced across an upper surface of the wafer from a central region of the wafer toward a periphery of the wafer, and is not displaced from the periphery to the central region.

TECHNICAL FIELD

The invention pertains to semiconductor processing methods of removingconductive material.

BACKGROUND OF THE INVENTION

Conductive materials are frequently formed over semiconductive materialsduring fabrication of semiconductor chips. In typical processing, acircular wafer of semiconductive material is processed to have one ormore thin conductive layers formed thereover. The conductive layers cancomprise, for example, metal (such as, for example, copper, aluminum,titanium, tantalum, iron, silver, gold, etc.) or other conductivematerials (such as, for example, conductively doped polysilicon). Theconductive materials can be subsequently planarized by, for example,electrochemical-mechanical planarization. In electrochemical-mechanicalplanarization, the conductive material is exposed to an electricalcircuit which causes at least some of the conductive material to beelectrochemically removed and the material is simultaneously exposed topolishing conditions. The polishing conditions enhance removal of theconductive material and planarize a surface of any remaining conductivematerial. The polishing can be accomplished by, for example, abrasivelyremoving the conductive material with a polishing pad and polishingslurry.

A difficulty associated with electrochemical-mechanical planarizationprocesses can occur in attempting to maintain a circuit through aconductive material during a simultaneous electrochemical removal andpolishing process. It is typical to utilize some portions of theconductive material for carrying current to other portions during theelectrochemical removal. For instance, peripheral edges of theconductive material can be connected to a cathode terminal of a powersource, a polishing pad connected to an anode terminal of the powersource, and the conductive material utilized to complete a circuitbetween the anode and cathode terminals. A problem which can occur asportions of the conductive material are removed is that such can breakan electrical connection to other portions of the conductive material.The breakage of the electrical connection can slow or stopelectrochemical removal of such other portions of the conductivematerial.

In particularly problematic instances, some portions of conductivematerial will be entirely removed from around other portions ofconductive material to leave such other portions as islands surroundedby electrically insulative materials. Such islands will thus have noelectrical connection between the anode and cathode, and will not besubjected to electrochemical removal conditions. Accordingly, theremoval of the islands will occur entirely through mechanical polishingand will be slowed relative to removal of conductive materials exposedto both electrochemical removal and mechanical polishing. Accordingly,there will be non-homogeneous removal of conductive materials from overa surface of a wafer.

It would be desirable to develop methods of electrochemical removal thatavoided some or all of the above-discussed problems.

SUMMARY OF THE INVENTION

In one aspect, the invention encompasses a semiconductive processingmethod of electrochemical-mechanical removing at least some of aconductive material from over a surface of a semiconductor substrate. Acathode is provided at a first location of the wafer, and an anode isprovided at a second location of the wafer. The conductive material ispolished with a polishing pad polishing surface. The polishing occurs ata region of the conductive material and not at another region. Theregion where the polishing occurs is defined as a polishing operationlocation. The polishing operation location is displaced across thesurface of the substrate from said second location of the substratetoward said first location of the substrate. The polishing operationlocation is not displaced from said first location toward said secondlocation when the polishing operation location is between the first andsecond locations.

In another aspect, the invention encompasses a semiconductor processingmethod of removing at least some of a conductive material from over asurface of a semiconductive material wafer. A polishing pad is displacedacross an upper surface of the wafer from a central region of the wafertoward a periphery of the wafer, and is not displaced from the peripheryto the central region.

In yet another aspect, the invention encompasses a method ofelectrochemically removing at least some of a conductive material fromover a surface of a circular semiconductive material wafer whichcomprises radially displacing a polishing pad across the surface of thewafer. The radial displacing occurs only outwardly from a central regionof the wafer and not inwardly toward the central region.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a diagrammatic, fragmentary, cross-sectional sideview of anapparatus utilized in accordance with a method of the present invention.

FIG. 2 is a diagrammatic top view of a semiconductive material waferprocessed in accordance with a method of the present invention.

FIG. 3 is a diagrammatic top view of a semiconductive material waferprocessed in accordance with a method of the present invention and shownalternatively to the view of FIG. 2.

FIG. 4 is a diagrammatic, fragmentary, cross-sectional sideview of anapparatus utilized for processing a semiconductive material wafer inaccordance with a second embodiment method of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

A process of the present invention is described with reference toapparatus 10 of FIG. 1. Apparatus 10 comprises a support structure 12having a semiconductor substrate 14 supported thereby. Substrate 14 cancomprise, for example, a monocrystalline silicon wafer. To aid ininterpretation of the claims that follow, the terms “semiconductivesubstrate” and “semiconductor substrate” are defined to mean anyconstruction comprising semiconductive material, including, but notlimited to, bulk semiconductive materials such as a semiconductive wafer(either alone or in assemblies comprising other materials thereon), andsemiconductive material layers (either alone or in assemblies comprisingother materials). The term “substrate” refers to any supportingstructure, including, but not limited to, the semiconductive substratesdescribed above.

Substrate 14 has an upper surface 15. Such surface can comprise, forexample, a surface of a semiconductive material wafer, or can comprise asurface of a material formed over a semiconductive material wafer. Forinstance, surface 15 can comprise a surface of an insulative materialformed over a stack of circuit devices associated with a semiconductivematerial wafer.

A conductive material 16 is formed over upper surface 15 of substrate14. Conductive material 16 can comprise, for example, a metal and/orconductively-doped silicon.

Substrate 14 has an outer peripheral edge 18 and a central inner region20. A polishing pad 22 is provided over central region 20 of substrate14. Polishing pad 22 is sized to extend over only a central portion ofconductive material 16, and to leave peripheral portions uncovered.Polishing pad 22 is supported by a support structure 24 which isconfigured to enable rotation of pad 22 about an axis “Y”.

Electrical connections 26 are provided along outer periphery 18 ofsubstrate 14 and electrically contact conductive material 16. Electricalconnections 26 are connected to a power source 28 which is alsoconnected to polishing pad 22. Power source 28 forms a circuit whichextends between polishing pad 22 and electrical connections 26 throughconductive material 16, and which utilizes polishing pad 22 as an anodeand connections 26 as a cathode. An electrolytic bath 30 is providedover conductive material 16 and between polishing bath 22 and electricalconnections 26 to complete the electrical circuit. Electrolytic bath 30can comprise, for example, an aqueous solution having salts dissolvedtherein. Bath 30 can also comprises abrasive particles for utilizationas polishing slurry during polishing of conductive material 16 withpolishing pad 22.

Although the embodiment of FIG. 1 shows electrolyte as being provided bya bath 30, it is to be understood that the electrolyte can be providedonly over surface 16 by, for example, flowing a stream of electrolyteonto surface 16. Such stream could be flowed, for example, through aporous polishing pad 22, or alternatively through a tube provided oversurface 16 and configured to allow the electrolyte to flow acrosssurface 16 and under pad 22. Also, a polishing slurry could be providedby flowing a stream of slurry over surface 16, rather than as materialwithin a bath.

Support 12 is configured to spin about an axis “Z” and to thereby spinsubstrate 14 and conductive material 16 relative to polishing pad 22.Polishing pad 22 comprises a surface 32 configured to abrasively removematerial 16 as the surface is moved relative to material 16. Inparticular embodiments, the abrasive action of surface 32 results frominteraction of surface 32 on a polishing slurry. In other embodiments,the abrasive action results from contact of surface 32 directly againstmaterial 16. Regardless of whether surface 32 contacts material 16directly and/or through a polishing slurry, the spinning of material 16relative to polishing pad 22 creates an abrasive action on material 16which causes removal of at least some of material 16. Since polishingpad 22 is sized to extend over only a portion of conductive material 16,polishing surface 32 has a smaller surface area than does material 16.

Although both pad 22 and substrate 14 are shown being rotated, it is tobe understood that the invention encompasses other embodiments whereinonly one of pad 22 and substrate 14 is rotated. Also, although pad 22 isshown being rotated in a counter-rotary manner relative to the rotationof substrate 14, it is to be understood that the invention encompassesother embodiments wherein the pad and substrate rotate in a commondirection relative to one another.

An electric current is provided within material 16 from power source 28during the polishing of the material with pad 22. Such electric currentcauses electrochemical removal of conductive material 16, and thusenhances removal of material 16 relative to the removal which wouldoccur by polishing action alone.

After at least some of conductive material 16 is removed from overcentral region 20 of substrate 14, pad 22 is displaced outwardly indirection “W” relative to substrate 14. Cathode 26 can be considered asbeing at a first location of substrate 14 and central region 20 can beconsidered a second location of substrate 14, and the displacement ofpad 22 along direction “W” can thus be considered a movement ofpolishing surface 32 from the first location of substrate 14 toward thesecond location. Preferably, polishing pad 22 is displaced only from thesecond location toward the first location, and not in the reversedirection. In such preferred embodiment, conductive material 16 isremoved from over a central location of substrate 14 prior to removingthe conductive material from over outer regions of substrate 14. Thus, acircuit extending between cathode 26 and the anode of pad 22 throughconductive material 16 can remain complete during removal of theconductive material 16. Specifically, since the inner (i.e., morecentral) portions of conductive material 16 are removed prior toremoving outer portions of conductive material 16, and since pad 22 isnot moved back over a more central region of conductive material 16after removing an outer region of conductive material 16, a bridge ofconductive material 16 can always remain between pad surface 32 andcathode 26 to maintain electrical conductivity between cathode 26 andpad surface 32 during removal of conductive material 16. Such canalleviate prior art problems discussed above in the “Background” sectionof this disclosure.

It is noted that although cathode 26 is shown at an outer periphery ofsubstrate 14 and the anode is shown starting at a central region ofsubstrate 14, the relative positions of the cathode and anode can bereversed. Also, it is noted that cathode 26 can be a single electrodeextending entirely around a periphery of substrate 14, or can comprise aplurality of electrode segments spaced around periphery 18 of substrate14. It is additionally noted that although polishing pad 22 is shownstarting at a central location of substrate 14, it is to be understoodthat the polishing pad could start at a different location of substrate14, provided that in a preferred embodiment the pad worked from thestarting location toward the cathode, and was not worked back toward thestarting location after it had left the starting location.

FIG. 2 shows a top view of substrate 14, and shows electrode 26 as acontinuous electrode extending around substrate 14. FIG. 2 also shows anexemplary path 40 for polishing pad 22 (FIG. 1). The pad starts at aboutcentral region 20 and spirals outwardly from central region 20 towardperiphery 18 of substrate 14. The shown substrate 14 is circular and hasradii 42 extending outwardly from a central location. The spiral path ofthe polishing pad moves the pad only outwardly along radii 42, and notinwardly. In other words, the polishing pad is moved only from centrallocation 20 outwardly toward periphery 18, and not inwardly back towardcentral location 20. A term “polishing operation location” is utilizedin this document to refer to locations wherein polishing is activelyoccurring. The movement of polishing pad 22 moves the polishingoperation locations across substrate 14 in the spiral pattern 40.

Direction “W” of FIG. 1 is shown in FIG. 2 to illustrate that the spiralpath 40 causes the polishing pad to be always moving outward fromcentral location 20 toward a point 44 on periphery 18 along direction“W” whenever the pad is between central location 20 and the locationcorresponding to point 44. It is also noted that when polishing pad 22is not between location 20 and point 44, the pad does not move alongdirection “W”, but instead moves in other directions which take the padoutwardly from central location 20 toward periphery 18. It is furthernoted that the spiral trajectory of path 40 defines concentric rings oftravel of the polishing pad, with such concentric rings extendingradially outward from central location 20.

The spiral pattern of FIG. 2 is but one pattern which can be utilized toprogress polishing operation locations across a substrate surface.Another pattern which could be utilized is in the form of distinct rings60, 62 and 64 shown in FIG. 3. Note that the more centrally occurringring 60 would preferably be formed first, followed by ring 62, andlastly by the most outward ring 64. Note also that the polishing padcould remain in abrasive contact with a surface of conductive material16 as the pad moves from one ring to another, or alternatively that thepad could be lifted from conductive material 16 during movement of thepad from one ring to another.

As was discussed above with reference to FIG. 1, one or both of apolishing pad and a wafer substrate can be rotated during displacementof the pad relative to the wafer substrate. It is to be understood thatrotation of either the pad or the substrate is not the same as“displacement” within the present application. Specifically, the term“displacement” is defined to refer only to situations in which apolishing operation location is moved across a wafer surface, and not tosituations wherein a polishing operation location remains at a samelocation over a wafer surface while a pad is being rotated or otherwisemechanically agitated. Also, it is to be understood that displacementcan occur by moving either a substrate, a polishing pad, or both asubstrate and a polishing pad, provided that the net result is movementof the substrate and/or pad relative to the other of the substrateand/or pad. Further, it is to be understood that displacement can occurwithout moving a polishing pad relative to a substrate, provided that alocation of a polishing operation is moved relative to the substrate.

An exemplary apparatus in which a polishing operation location isdisplaced without displacement of a polishing pad is described withreference to FIG. 4. In referring to FIG. 4, similar numbering will beused as was utilized above in describing the apparatus of FIG. 1, withthe suffix “a” used to indicate structures shown in FIG. 4.

FIG. 4 shows an apparatus 10 a comprising a substrate holder 12 a and asubstrate 14 a supported by holder 12 a. A conductive material 16 a isformed over substrate 14 a and extends across an upper surface ofsubstrate 14 a. Substrate 14 a has a central region 20 a and aperipheral region 18 a, and comprises at least one electrode 26 aconnected to conductive material 16 a along periphery 18 a. Aflexible-material polishing pad 22 a is provided over conductivematerial 16 a. A narrow structure 24 a (shown as a post) is providedover a location of pad 22 a and pushes a region of pad 22 a againstconductive material 16 a. Pad 22 a is electrically connected to a powersource 28 a, which in turn is connected to electrode 26 a.

In operation, post 24 a is utilized to press a portion of large pad 22 aagainst a region of conductive material 26 a, and subsequently substrate14 a is rotated relative to pad 22 a to cause abrasion of material 26 ain a location pressed against pad 22 a. Also, power source 28 a isutilized to provide current through conductive material 16 a duringrotation of substrate 14 a, and thus to facilitate electrochemicalremoval of material 16 a in conjunction with the abrasive polishing.

Pad 22 a can be supported by post 24 a such that the pad and post aremoved over conductive material 16 a in, for example, a spiral patternsimilar to that shown in FIG. 2. Alternatively, pad 22 a can beseparately supported so that the pad remains in a fixed location andpost 24 a is displaced over the pad to cause different portions of thepad to be pushed against spinning substrate 14 a. Post 24 a could bemoved, for example, in a spiral pattern such as that shown in FIG. 2. Inembodiments in which pad 22 a remains stationary during the movement ofpost 24 a, a location of a polishing operation is displaced relative tosubstrate 14 a by displacement of post 24 a, and without displacement ofpolishing pad 22 a. The peripheral edges of pad 22 a are shown raisedrelative to the center of pad 22 a. Such configuration can be achievedby utilizing a pad material having an inherent flex of its peripheraledges relative to its center region, or by attaching one or more supportstructures (not shown) to the peripheral edges of the pad to raise theedges. Alternatively, the pad can be formed of a flexible material whichlays flat across surface 16 a, but which is in non-abrasive contact withthe surface in regions which are not pressed between post 24 a andsurface 16 a.

It is noted that in the above-described embodiments of FIGS. 1 and 4only a portion of conductive material 16 is exposed to abrasivepolishing at any given time during an electrochemical polishing process.Accordingly, some portions of a conductive material (16 or 16 a) are inabrasive contact with a polishing pad (22 or 22 a), and other portionsare not in such abrasive contact during an electrochemical polishingprocess. As the polishing process progresses, the portions which had notbeen in abrasive contact become in abrasive contact while the portionsthat had been in abrasive contact are no longer in abrasive contact withthe polishing pad. Preferably, once a portion progresses from being inabrasive contact with a polishing pad to not being in abrasive contactwith the polishing pad, it is no longer exposed to electrochemicalpolishing conditions during the remainder of the electrochemicalpolishing process.

The above-described electrochemical polishing processes can be followedby conventional chemical-mechanical polishing processes to buff asubstrate after the electrochemical polishing. The chemical-mechanicalpolishing comprises polishing with a polishing pad and slurry, and isnot electrochemical polishing.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

What is claimed is:
 1. A semiconductor processing method ofelectrochemical-mechanical removing at least some of a conductivematerial from over an upper surface of a semiconductor substratecomprising displacing a polishing operation location across the uppersurface of the substrate from a central region of the substrate toward aperiphery of the substrate and not displacing the polishing operationlocation from the periphery to the central region.
 2. The method ofclaim 1 wherein the polishing operation location is defined by alocation of a polishing pad relative to a surface of the substrate, andfurther comprising rotating the polishing pad separately from thedisplacement.
 3. The method of claim 2 wherein an electrical circuit isprovided through at least a portion of the conductive material duringthe removing, the circuit extending between at least one secondelectrical connection in electrical contact with a polishing surface ofthe polishing pad and at least one first electrical connection in directelectrical contact with conductive material only at the periphery. 4.The method of claim 2 wherein the displacing comprises moving thesubstrate relative to the polishing pad.
 5. The method of claim 2wherein the displacing comprises moving the polishing pad relative tothe substrate.
 6. The method of claim 2 wherein the displacing comprisesmoving both the polishing pad and the substrate.
 7. The method of claim1 further comprising, after the electrochemical-mechanical removing,chemical-mechanical polishing of the substrate utilizing a process thatis not electrochemical-mechanical polishing.
 8. A semiconductorprocessing method of electrochemical-mechanical removing at least someof a conductive material from over a surface of a circularsemiconductive material wafer comprising radially displacing a polishingpad across the surface of the wafer, the radial displacing being onlyoutwardly from a central region of the wafer and not inwardly toward thecentral region.
 9. The method of claim 8 wherein the polishing pad isdisplaced circularly around the central region to define rings whichprogress increasingly outward toward a periphery of the wafer.
 10. Themethod of claim 9 further comprising rotating the polishing padseparately from the displacement.
 11. A semiconductor processing methodof electrochemical-mechanical removing of at least some of a conductivematerial from over a surface of a semiconductor substrate comprising:providing a substrate having a conductive material thereover; providinga cathode at a first location of the substrate; providing an anode at asecond location of the substrate, the anode being associated with apolishing pad polishing surface; polishing the conductive material withthe polishing pad polishing surface, the polishing occurring at a regionof the conductive material and not at another region, the region wherethe polishing occurs being defined as a polishing operation location;and displacing the polishing operation location across the surface ofthe substrate from said second location of the substrate toward saidfirst location of the substrate, and not displacing the polishingoperation location from said first location toward said second locationwhen the polishing operation location is between the first and secondlocations.
 12. The method of claim 11 wherein the second location ismore centrally located on the substrate than the first location.
 13. Themethod of claim 11 further comprising rotating at least one of thepolishing pad and the substrate separately from the displacement. 14.The method of claim 11 wherein the polishing pad is pressed between astructure and the substrate, and wherein the displacing the polishingoperation location comprises displacing the structure relative to thepolishing pad.
 15. The method of claim 11 wherein the polishing pad onlycovers a portion of the conductive material, and wherein the displacingthe polishing operation location comprises displacing the polishing padrelative to the substrate.
 16. The method of claim 15 wherein thedisplacing comprises moving the substrate relative to the polishing pad.17. The method of claim 15 wherein the displacing comprises moving thepolishing pad relative to the substrate.
 18. The method of claim 15wherein the displacing comprises moving both the polishing pad and thesubstrate.
 19. A semiconductor processing method of removing conductivematerial, comprising: providing a semiconductor wafer having aconductive material thereover, the wafer comprising an upper surface andan outer periphery around the upper surface, the conductive materialextending across the upper surface of the wafer and to about theperiphery; electrochemically removing at least some of the conductivematerial with a polishing pad having a surface in abrasive contact withonly a portion of the conductive material; and displacing the polishingpad across the upper surface of the wafer during the removing, thedisplacing being only from a central region of the wafer surface towardthe periphery of the wafer.
 20. The method of claim 19 wherein thepolishing pad is displaced circularly around the central region todefine rings which progress increasingly outward toward the periphery ofthe wafer.
 21. The method of claim 19 further comprising rotating thepolishing pad separately from the displacement.
 22. The method of claim19 wherein an electrical circuit is provided through at least a portionof the conductive material during the removing, the circuit extendingbetween at least one second electrical connection in electrical contactwith a polishing surface of the polishing pad and at least one firstelectrical connection in direct electrical contact with conductivematerial only at the periphery.
 23. A semiconductor processing method ofremoving conductive material, comprising: providing a semiconductorwafer having a conductive material thereover, the wafer comprising anupper surface and an outer periphery around the upper surface, theconductive material extending across the upper surface of the wafer andto about the periphery; electrochemically removing at least some of theconductive material with a polishing pad having a surface in abrasivecontact with only a portion of the conductive material, the portion ofthe conductive material in abrasive contact with the surface beingdefined as polishing operation location, the polishing pad extendingover the conductive material to cover more of the conductive materialthan the polishing operation location; and displacing the polishingoperation location across the upper surface of the wafer during theremoving, the displacing being only from a central region of the wafersurface toward the periphery of the wafer.
 24. The method of claim 23wherein the polishing operation location is displaced across the uppersurface of the wafer without displacing the polishing pad.
 25. Themethod of claim 23 wherein the polishing operation location is displacedcircularly around the central region to define rings which progressincreasingly outward toward the periphery of the wafer.
 26. The methodof claim 23 further comprising rotating the wafer separately from thedisplacement.
 27. The method of claim 23 wherein an electrical circuitis provided through at least a portion of the conductive material duringthe removing, the circuit extending between at least one secondelectrical connection in electrical contact with a polishing surface ofthe polishing pad and at least one first electrical connection in directelectrical contact with conductive material only at the periphery.
 28. Asemiconductor processing method of removing conductive material,comprising: providing a semiconductor wafer having a conductive materialthereover, the conductive material defining a surface area, the surfacearea having a first portion surrounded by a second portion; providing apolishing pad surface in abrasive contact with the first portion of theconductive material surface area and not in abrasive contact with thesecond portion of the conductive material surface area; providing acircuit that extends across at least some of the first portion of theconductive material surface area to the second portion;electrochemically removing at least some of the conductive material fromthe first portion of the surface area by polishing the first portionwith the polishing pad while flowing current through the circuit; afterelectrochemically removing the at least some of the conductive materialfrom the first portion, displacing the polishing pad relative to thewafer and electrochemically removing at least some of the conductivematerial from the second portion surrounding the first portion; and notelectrochemically removing conductive material from the first portionafter electrochemically removing conductive material from the secondportion.
 29. The method of claim 28 wherein the first portion of theconductive material surface area is more centrally located on the wafersurface than the second portion of the conductive material surface area.30. The method of claim 28 further comprising rotating at least one ofthe polishing pad and the wafer separately from the displacement. 31.The method of claim 28 wherein the displacing comprises moving the waferrelative to the polishing pad.
 32. The method of claim 28 wherein thedisplacing comprises moving the polishing pad relative to the wafer. 33.The method of claim 28 wherein the displacing comprises moving both thepolishing pad and the wafer.
 34. A semiconductor processing method ofelectrochemically removing conductive material, comprising: providing asemiconductor wafer having a conductive material thereover, theconductive material defining a first surface area, the first surfacearea having a central portion and an outer peripheral portionsurrounding the central portion, the outer peripheral portion having anoutermost edge; providing at least one first electrical contact inelectrical connection with the outermost edge of only the outerperipheral portion of the conductive material; providing a polishing padproximate the central portion of the conductive material, the polishingpad having a polishing surface, the polishing surface defining a secondsurface area, the second surface area being less than the first surfacearea; providing at least one second electrical contact in electricalconnection with the polishing surface of the polishing pad, the firstand second electrical contacts being in electrical connection through apower source and defining a circuit that extends through the conductivematerial; electrochemically removing at least some of the conductivematerial from the central portion by polishing the wafer with thepolishing pad while flowing current through the circuit; and only afterelectrochemically removing at least some of the conductive material fromthe central portion, displacing the polishing pad relative to the waferto provide the pad proximate the outer peripheral portion of theconductive material and utilizing the polishing pad to electrochemicallyremove at least some of the conductive material from the peripheralportion, but not displacing the polishing pad from the outer peripheralportion to the central portion.
 35. The method of claim 34 wherein thedisplacing comprises moving the polishing pad circularly around thecentral region to define rings which progress increasingly outwardtoward the peripheral portion of the wafer.
 36. The method of claim 34wherein the displacing comprises moving the wafer relative to thepolishing pad.
 37. The method of claim 34 wherein the displacingcomprises moving the polishing pad relative to the wafer.
 38. The methodof claim 34 wherein the displacing comprises moving both the polishingpad and the wafer.